1. Field of the Invention
The present invention relates to the application of zippers to film used to make reclosable plastic bags. More specifically, the present invention relates to a roller-type zipper applicator with a zipper guide in which a disc with a circumference greater than at least one of the rollers of the applicator is positioned on the end of the roller with the smaller circumference.
2. Description of the Prior Art
The present invention relates to improvements in the package-making art and may be practiced in the manufacture of reclosable thermoplastic bags and packages of the type that may be used for various consumer products. Such packages often include a form of peel-seal to render the package moisture and/or airtight prior to the initial opening and/or as a tamper-evident seal. A zipper means protects any remainder of the product therein after the initial opening.
The indicated art is fairly well developed but nevertheless remains open to improvements contributing to increased efficiency and cost-effectiveness in the package-making art. In the prior art, McMahon et al. (U.S. Pat. No. 4,909,017) discloses a method of making a form-fill bag having a reclosable fastener. Prior to entering a form-fill and seal (FFS) machine, fastener strips are attached to the surface of the film at bag length intervals transverse to the running direction of the film. The fastener strips contain pre-joined interlocked rib and groove strips. Only one of the strips is attached to a top surface of the film, with the other strip facing upwardly or, in other words, inwardly toward the interior of the bag to be formed. The attached strips are secured at the center of the film and each strip is less than half of the film's width. The film is then advanced to the FFS machine and drawn over a forming collar and about the filling tube, with the longitudinal side edge margins of the film brought together and seamed with a fin seal to form a tube. Cross-seals are made across the tube to join the unattached fastener strip to form the top and bottom of the bag.
A problem is sometimes encountered during the attachment of the fastener or zipper to the film. Typically a roller-type zipper applicator engages one profile of the zipper and positions the zipper on the film used on the FFS machine. The other profile of the zipper is interlocked with the engaged profile and moves to be later attached to the film as a result of the profiles being interlocked. However, if the profiles are not securely interlocked or longitudinally slide against each other, the profiles may significantly misalign in relation to each other as the roller moves the profile on which it is engaged. This misalignment of the zipper profiles makes it difficult to properly seal the zipper to the film, resulting in a defective zipper after formation of the reclosable bag. An improvement in the zipper applicator would be the ability to engage both profiles with at least one or more rollers of the zipper applicator in order to calibrate the movement of both profiles to the movement of the rollers. The calibrated movement of both profiles would prevent the zipper profiles from misaligning with each other before attachment to the film used to make a reclosable bag.